The current widespread therapeutic application of biofeedback is based more on untested assumptions than on scientific evidence. The proposed 3-year project is designed to provide such evidence by conducting basic research on the major issues and assumptions underlying use of the technique. The project will intensively evaluate the two major modalities of biofeedback (electromyographic, EMG and skin temperature, ST) for the purposes of: (1) establishing adequate criteria to define physiological learning, (2) assessing the role of placebo and expectational effects, and (3) examining the ability to exert volitional control over physiological activity under stress-avoidance conditions. Normal college-age volunteers will participate in the three phases of the project. In phase 1, a double-blind, yoked-control study of EMG biofeedback will be conducted using real and placebo feedback groups, as well as a motivated relaxation control group. Controls for effects due to general relaxation, drowsiness and habituation will be included. This identical study will be repeated in the third phase to evaluate ST biofeedback, with additional controls specific to ST. The middle phase will use a new experimental paradigm to evaluate the ability of subjects to: (1) self-regulate EMG activity over a broad range, (2) exert volitional control without feedback, and (3) exert volitional control under stress-avoidance conditions. The findings will provide a much clearer understanding of factors underlying current applications of biofeedback and the role of physiological self-regulation in health and disease. Such increased understanding may lead to improvements in the efficacy of future uses of the techniques.